The objective of this proposal is to determine the microenvironmental factors responsible for tumor recurrence following therapy and to discover the underlying mechanisms. Previous studies have shown that tumor cells travel to sites of radiation as well as surgical scars from tumor excision, which leads to the hypothesis that the tumor microenvironment encourages circulating tumor cell migration following radiation and surgical therapies. This hypothesis will be tested using pre-clinical orthotopic breast cancer models to study how the microenvironment responds to radiotherapy and surgery and potentially influences cancer cell migration. My project is guided by three specific aims: (1) To determine how tumor-stromal interactions affect tumor cell migration, (2) to understand the role of the immune system in facilitating tumor cell migration, and (3) to investigate molecular pathways and biomechanical properties in the tumor microenvironment following therapy. A combination of biological, bioengineering, and imaging techniques will be used to evaluate the stated specific aims. Luciferase- and tdTomato-labeled human and mouse mammary carcinoma cells will be used to form orthotopic breast cancer models in mice. The course of tumor growth and migration after both radiation and surgery of normal tissues will be examined using bioluminescence imaging. Immune cell infiltration and distribution in treated areas will be assessed using immunohistochemistry and flow cytometry to identify recruited macrophages and myeloid derived suppressor cells. Granulocyte macrophage stimulating factor, an inflammatory cytokine known to play a role in tumor cell migration following radiation, will be monitored in both preclinical mouse and patient blood samples before and after therapy. Finally, changes in the tumor microenvironment after radiation and surgical therapy will be analyzed to determine factors that induce tumor cell migration. RNAseq will be used to evaluate the regulation of critical pathways involved in tumor cell migration and invasion. The mechanical properties of tissues following therapies will also be analyzed to discern the link between biological factors and physical cues in cancer progression and recurrence. Taken together, the results of these experiments will lead to the design of biomimetic tumor microenvironment models. Dr. Rafat's immediate goal is to determine whether microenvironmental response plays a role in modulating metastasis and relapse after therapy. This project will identify molecular mechanisms that influence tumor cell migration and invasion and examine the effect of interventional therapies themselves in facilitating disease progression. This work will lay the foundation for Dr. Rafat to establish an independent laboratory at an academic research institution. Her training program includes attendance at relevant seminars, workshops, and courses hosted by Stanford University as well as oversight from a mentor, co-mentor, and respected Career Advisory Committee to supervise both career and scientific development.